PowerSwitch

About a year ago, our company had a survey done by the Carbon Trust, which carries out a similar role for business that the Energy Savings Trust does for private households.

We have a fair number of halogens in use at our sites. Many are in foyers, lift areas and stairwells and seem to be on 24/7. The Carbon Trust told us that if we used dimmers to reduce the light levels by 10%, we'd get a 30% saving in energy use. I accepted this without questioning at the time (very remiss of me I know!) but it seems unlikely.

I thought that dimmers worked the other way: e.g. a 30% reduction in light levels would only give a 10% reduction in energy use. Does the power factor of the equipment in use have any bearing here? Any thoughts or advice to help me understand this better?

Adam

p.s. Needless to say, the company has done nothing in the meantime to reduce the energy used to light our premises!

They are wrong !
This is not simply my opinion, but may be readily confirmed by the use of a wattmeter and a lightmeter.
The already poor efficiency of halogen lamps will be made even worse by dimming them.
Dimming a halogen lamp will certainly reduce the power used, but the light output will reduce even more. A 10% reduction in wattage via a dimmer, will reduce the light output by about 50%. The human eye is not good at measuring such changes, and as a result it may not look like 50%, but it is!
Idealy the halogen lamps lamps should be replaced by something more efficient.
If halogen is allegedly essential fot aesthetic reasons, then they should be wired on two circuits, one of which can be turned off at times of no/reduced occupancy.

Thanks for that Adam. I will feed that info back to my colleagues.

The advice seems counter intuitive and is almost certainly wrong but I think you need to look into it in a little more detail. Do they explain how they expect this saving to work?

For LV Halogens one possible saving that can be made is switching from electromagnetic to electronic power supplies (noises of muttering, coughing and power factor stage left). This can make a big difference as the efficiency of some of the electromagnetic gear is pretty poor. For a 12V 45W lamp the the power used on the prrimary of the transformer can be as high as 80W.

If for some reason you must have the halogen (sparkle?) then there are HID alternatives which come close. The luminaire we use the 45W halogen lamp above in also comes with a mini metal halide lamp rated at 35W which is as bright as if not brighter than the 45W halogen, the gear to run it is electronic and only draws 48W, the downside is it's a lot more expensive to replace the lamps (factor of ten).
If you stick with Halogen then drop the lamp size, some manufacturers now produce lamps which produce higher light output for a given wattage. For example a 30W lamp which has the same output as a 50W standard dichroic lamp or so it says on the box.

In support of Adams point, if you drop the power by dimming you will find that even the more efficient (for Halogen) lamps lose their advantage, they run well by running hot.

For the record I work for a lighting company as a development engineer. The information above is I hope generic enough not to be seen as promoting my employer. If you want any specific information then please message me and I'll try my best to help.

revdode wrote:
For LV Halogens one possible saving that can be made is switching from electromagnetic to electronic power supplies (noises of muttering, coughing and power factor stage left). This can make a big difference as the efficiency of some of the electromagnetic gear is pretty poor. For a 12V 45W lamp the the power used on the prrimary of the transformer can be as high as 80W.

On the other hand I believe if you have electromagnetic txformers you also have the option of saving energy by using these (cfl equivalents):
http://www.initiallights.co.uk/index.php?cPath=26

revdode wrote:
For the record I work for a lighting company as a development engineer.

So you can correct me if I'm wrong

Never come across that before but from the FAQ it reads like they need their own dedicated PSU rather than running direct from a Halogen transformer.
Again with CFL the overall system efficiency depends a lot on the gear used to the power the lamp. I'll try and find out more but it certainly isn't a product I'm familair with.

I have just measured the power consumed by a standard (copper iron, not electronic) halogen transformer feeding two lamps each of 12 volts 50 watts.
Total consumption was 118 watts, which is fairly typical. Electronic transformers are more efficient than that, though the savings wont be huge, unless of course the existing transformers are much worse than average.
the nominal 50 watt lamps only appeared to be 48 watts each, though that might be instrument error.

Our company has two problems (relating to energy saving and lighting anyway!):

1 - we are currently spread over four sites most of which need some sort of general refurb. Unfortunately, the company seems unwilling to make any strategic decisions about how to house its staff in a rationalised one or two site solution. Because of this indecision, it is hard to get them to invest significantly in any new fixtures for the existing sites.

2 - our colleagues in facilities management (I don't work in FM but am working informally with them, together with a group of concerned colleagues, on green issues) don't have any in-depth technical knowledge that I can see and neither do I.

My thoughts were that we could do a simple replacement of low efficiency bulbs with CFLs and LEDs where that makes sense. We have a mixture of halogens, mostly flush ceiling mounted (12v and 240v), a few incandescents and office normal strip lighting units, the latter look pretty up to date with four 18W bulbs in reflective backing units. My tactic was going to be to get all the halogens replaced with LEDs or CFLs and to find out if some sort of retro-fitting of motion/light/sound sensors could be used for less frequently used and self-contained spaces. On the few occasions I've come into the office on a Saturday most lights do appear to be switched off.

Any change that involves changing the power supplies or any significant re-wiring is going to be harder to push forward. Last time we talked about getting automated light sensors, they said they'd looked into it and it was very expensive (code for "it ain't gonna happen mate").

RenewableCandy wrote:...
http://www.initiallights.co.uk/index.php?cPath=26

These LEDs look interesting. From the description, they provide a brighter and warmer light than the other LEDs I've seen to date.

They claim they are brighter than 20W halogens, so if we take that to mean roughly 25W, they are about 80% more efficient if they are rated at 5W. Sounds less efficient than I'd expect from an LED.

PRODUCT SPECIFICATION

* LIGHT SOURCE 3 x 1W High Power LEDs (total power consumption is 5 watts)
* OPTICS Glass Optic
* BEAM ANGLE 80? (Wide Angle Spot)
* Color Render Index(CRI) > 7 0 % (Warm White Color)
* WEIGHT 40g
* HOUSING Aluminium alloys
* BASE PC, flammability: V2 level
* TEMPERATURE RANGE Ambient: -20 ? C to 40 ? C; Surface of Lamp: 60 ? C to 65 ? C
* HUMIDITY RANGE 0 to 95% non-condensing humidity
* VOLTAGE REQUIREMENT AC/DC 12V 50/60 HZ
* POWER CONSUMPTION 5 W

Check out this...

http://www.globefox.com/vospad/gallery.html

All Leds, I think it's about 300 watts for the whole flat, and any colour you feel like. a bit 'Las Vegas' for my taste, but it shows what can be done.

I get the impression that presently LEDs are no more efficient (Lumens per watt) than CFLs but that, unlike CFLs, their efficiency is improving as Technology Marches On. Look out for owt that's verifiably more than 80 Lumens per Watt, though your chances of seeing anything quite so technical are pretty remote

I don't know the Cree products that well but generally high output LEDs do not respond well to running on a standard 12V Halogen PSU. I'd be concerned about the lamp life and colour stability of these unless they are driven by a supply designed to power LEDs. A one year warranty on a lamp that costs ?25 would worry me, but then I am Scottish.